Method of forming die-castings.



6. PACK.

METHOD OF FORMING DIE CASTINGS.

APPLICATION FILED JUNE 6, I918.

WWW, I

Patented Apr. 8, 1919.

2 SHEETS-SHEETI ATTORNEY C. PACK.

METHOD OF FORMING DIE CASTIN GS.

APPLICATION FILED wuss. I9l8.

l ,299L769, Patented Apr. 8, 1919.

. I 2 SHEETSSHEET 2- W whim IHWH' WW I W; I

H INVENTOR 7 H5 MV/AA I i3 7 MI I?! Q ATTjE'Y TO all wkom'it may cohcem:

ES PACK, OF BROOKLYN, NEW YORK,ASSIGNOR TO DOEHLER DIE CASTING COMPANY,-OF BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

mn'rnon or romaine DIEI-CASTINGS.

Be it known that I, Or'mmns PACK, a

. citizen of the United States, residing in the manufacture.

borough of Brooklyn,'county of Kings, and

State of New York, have invented certain .new and useful Improvements in Methods of Forming Die-Castings, of which the following is a specification.

My invention relates to amethod of forming die castings whereby the formation of cracks 'in the same because of shrinkage stresses will be obviated, and to the castings made by such method as new articles of When a sheet or wall of metal is cast between metal dies and the end portions of the same, or portions'at some distance from each other are held during the process of casting, so as to prevent shrinkage of the part, considerable stresses cooling ofthe casting, it will be obvious that the wall-or part will be held against movement in the mold between such ofi'set portions. The metals used for making die castings all have a shrinkage which may be computed as a constant factor perinch of length uponthe transition of the metal from the molten to the solid state, and a further shrinkage, the amount of which per inch may readily be figured, during the cooling from the temperature at which the metal solidifies to that at which the casting is removed from the mold. In the case of a wall or part having considerable extent and comparatively thin section, the stresses thus set up when the part is held from decreasing in length in the mold are considerable, and

' these stresses cause a pull at a point in the wall or part which for some reason may be a weak point, suflicient in many cases to cause a crack at such point. It is evident that the pull at such point will be of an amount equal to the pull per unit length multiplied by the length through which the stress is permitted to act, and the case of a wall having smooth surfaces and held at its ends, the pull-or stress at a given distanc from an end will be equal to the stress per Specification of Letters Patent.

Patented Apr. 8, 1919.

Application filed June s, 1918. Serial No. 238,481.

-which' projections may be very slight in height, such, for example, as slight ribs formed on the face ofthe wall at right angles to the direction of the stress. Such projections form points of anchorage between the casting and the adjacent die member, so that -the shrlnkage stresses in the. -member w1ll be sub-divided in accordance withthe number and spacing of such pro 'jections. Thus, for example, if a wall be six inches in length and held at its ends, and if twelve equally spaced ribs are provided between the ends of the wall, the shrinkage stress between anyadjacent pair of projections, or between the end wall of the casting and the adjacent projection will be only onetwelfth ,of the total shrinkage stress developed within thepart or wall, all of which stress would exert a pull at one weak point in the wall if the surfaces of the same were smooth. I am, of course, aware of the fact that ribs or projections are often formed on die castings for stiffening purposes; or for the purpose of performing some other function in relation to' the use for which the casting is intended. My invention does not include the use of such projections, but, on

the contrary, relates 'to the production of slight projections on surfaces which would otherwise be smooth, and which projections are intended to serve no useful end other than to distribute and sub-divide the shrinkage stresses in the part.

In order that a clearer understanding of my invention may be had, attention is hereby directed to vthe accompanying drawings forming part of this application and illustrating certain embodiments of my invention. In the drawings, Figure 1 represents a top plan view of a casting formed in accordance with my invention, Fig. 2 is a longitudinal section thereof taken on line 22 of Fig. 1, Fig. 3 is a transverse section taken on the line 3-3 of Fig. 2, the casting being shown as still within the die in which it is at the bottom thereof. The inner. surface of 1. In the method of form ng die castings,

- side wall 4 and by a curved side wall 5, hav;

ing apertured lugs orjoflset portions 6, 6

the bottom portion 2 would normally be entirelysmooth, and because of its-large ex tent relative to its cross section, considerable shrinkage stresses develop therein during the solidification and cooling of the casting. Iv have shown this bottom portion 2 as protect ed against such shrinkage stressesby forming thereon a plurality of spaced 1ongitudi- I nal ribs Z, 7 of slight height-and a plurality of spaced transverse ribs 8, which may extend between the ribs 7 7 to form a sort of lattice work, as shown. The casting is shown in Fig. 3 as still within the parts 9, 9' of the die from,which is evident the manner in which the bottoni wall 2 is restrained from shrinking lengthwise between the end walls 3, 3 and also the manner in which the ribs 3 7 7 anchor the bottom portion 2 to the. die

member 9' and thereby sub-divide the stresses in bottom member 2 between the walls 3, 3.

In Figs. 4, 5 and 6 a rectangulan frame member 10 is shown, the four sides of which are provided with "ertical web portions 11,

'11 and with top'fiange portions 12, 12. The

web portions are provided at various points with vertical ribs 13, which are of consider-- able size, and are provided for the purpose of stifiening the casting or for serving some other purpose in connection with the use for which the casting is intended. In accordthe shrinkage stresses in ance with my invention, I provide the vertical ribs 14, 14 on the inner surfaces of the webs 11 regardless of whether or not the stiffening ofl'sets or lugs 13 are or are not used. The ribs orpro ectionS 14' are of slight height-and width, are formed on surfaces which would gtherwise be smooth and have no purpose other than to sub-divider the manner indil same purpose, are provided at suitably the "metal of the casting, the distance between ofi'set portions of the walls of the casting and the other physical factors of the problem. A

What I claim is ma Q Rib 14, or otherprojections for the spaced; intervals, *which'may be calculated 7 'with regard to the shrinkage coeflicients of tion in relation to the useful purpose ofthe casting formed, but are provided on a surfacewhich would otherwise be smooth.

2. Inthemethod" of forming die castings,

which comprises forming between rigid dies a metal casting having a wall of considerable extent in proportion to its thickness,

with ofi'set portions at the extremities thereof, the step of providing ribs of slight heights:

on one of the faces of said wall ,"at spaced intervals between said ofi'set port1ons, transversely to the direction of the shrinkage stresses between said offset portions, by so forming one of the dies as to' forni said ribs .on said wall, and'thereby sub-divldlng the stresses tending to crack said wall between said offset portions, when thecasting solidifies in the mold and cools, said rlbs being formed onasurfacewhich would otherwlse be smooth, being unnecessary for stifi'ening purposes, and having no relation to the use- .ful purpose of the casting formed. This specification signed and witness this 3rd day of June, 1918. CHARLES PACK. Witnesses:

' EDMUND J. WARD,

Gno. L..Mooi:n. 

